Improvement of color and color stability of saturated fatty acids



Patented Jan. 22, 1952 IMPROVEMENT OF COLOR AND COLOR STA- BILITY OF SATURATED FATTY ACIDS David E. Terry and Donald T. Warner, Minneapolis, Minn.,' assignors toGeneral Mills, Inc., a

corporation of Delaware No Drawing. Application November 13,, 1950, Serial No. 195,462

3 Claims. (Cl. 260-398.5)

The present invention relates to the preparation of saturated higher fatty acids having improved color and color stability.

For many uses to which higher saturated fatty acids are put, it is essential that the fatty acids possess a light color and that the color be stable over long periods of time. Fatty acids for such uses are commonly produced by the fractional distillation of hydrolyzed animal and vegetable oils, or from waste products resulting from the processing of such oils. duced, these fatty acids have a fair degree of whiteness but are not sufficiently light in color to be used for many industrial applications. It is essential, therefore, to improve the initial color of these fatty acid products.

While the fatty acids mitially produced by distillation may have a fair color, this color rapidly deteriorates on storage and the product'after a reasonable storage period possesses such a poor color that it can be used only for uses which command a low price.

This degradation in color is apparently caused by certain color forming bodies which are present in the fatty acids initially, but which are colorless at that point. Upon exposure to air and light these color forming bodies are converted into compounds which are colored and which thus color the entire body of fatty acid.

It is essential, therefore, to treat these fatty acid products not only to improve their initial color, but to give the'fatty acid products'color stability for a long period of time.

l-leretofore the improvement in color of fatty acids and fatty products has been accomplished by various bleaching methods, principally by means of the use of various bleaching agents such as the bleaching earths, activated carbon, and the like. These methods have been subject to various disadvantages. The bleaching agents employed are relatively expensive and in their use they entrain considerable quantities of the fatty acids being treated thereby reducing the tion to provide a novel process of treating higher saturated fatty acids with boron trifiuoride to improve the initial color and to improve the color stability of the fatty acids.

The process comprises the treatment of higher saturated fatty acids with a small quantity of boron trifiuoride at a temperature within the approximate range of 70-200 C. for a time period of 2 to 4 hours. Small quantities of boron tri fluoride are sufficient to accomplish the desired results. Thus A; of 1% by weight of boron trifluoride based on the weight of the fatty acid is sufficient to produce a material improvement in color and color stability. One-half of l% by weight of boron trifiuoride is usually sufficient to accomplish the maximum improvement of color and color stability. Quantities of boron trifluoride in excess of of 1% may be used but the improvement in results from the use of the excess usually does not justify the increased cost. The boron trifluoride may be used in the form of boron trifluoride itself, which is a gas. It is usually more convenient, however, to employ the boron trifiuoride in the form of its ether complex, in which case it will be appreciated that a sufiiciently increased quantity of the complex should be employed to provide the desired quantity of boron trifluoride.

4 At the lower portion of the temperature range, the time required is in the upper portion of the time range, and accordingly it is preferred-to carry out the process at temperatures within the range of 1501'75 C. at which temperatures the time required is in the lower portion of the time range.

The treatment involves the admixture of the boron trifluoride with the fatty acid while the latteris in a liquid condition. In the case of fatty acids which are liquid at normal temperature, the admixture may be effected at room temperatures. In the case of the higher melting fatty acids, these may be melted first and the boron trifiuoride added thereto. The resulting mixture is then heated to temperatures within the range mentioned above and agitated for the time period described. Following the treatment, the mixture is cooled to about 100 C. and then washed with water until the boron trifiuoride is removed. The product is then dried and subjected to distillation. The product obtained upon distillation is much improved in color, in color stability on aging, and in color stability on heating to 205 C.

In the following examples the Coleman Junior spectrophotometer was used for the determination of the color of the samples. Color of the samples was determined at five wave lengths- 400, 425, 450, 475, and 500 millimicrons. The color values are stated in percentage transmittance compared with distilled water values: 100 at each of the wave lengths. Thus, for

example, a tube of distilled water was placed in the instrument and the instrument was adjusted such that the reading was equal to 100% at that wave length. Then the distilled water tube was removed and the fatty acid sample was placed in the instrument. The instrument reading was then recorded as a measure of the fatty acid color at that wave length. The instrument readings at the five wave lengths were then averaged numerically and this average figure was designated as the color value in these examples.

In the heat stability test the color of the sample was first determined and the color value was recorded. The melted sample was then poured into a 50 ml. Nessler tube and heated for 2 hours at 205 C. The color of the heat treated sample was again determined in the spectrophotometer and the value was expressed as the color value after heating.

The storage of the fatty acid samples for the tests. after 1, 2 and 4 weeks was accomplished by flaking the fatty acid samples and then storing them in glass bottles with free exposure to the air. These samples were tested at intervals for color stability both before and after heating at 205 C. 7

Example 1 Treated and Freshly Distilled Pefore Flaked Product Treatment 1 Week 2 Weeks 4 Weeks As melted After heating 2 hours at 205 C.

Control: Freshly distilled and untreated, 77.

Freshly distilled and untreated, heated 2 hours at 205 0., 39.

Example 2 One hundred parts by weight of a commercial distilled palmiticacid and 1 part by weight of boron trifluoride ethyl ether complex were heated for 4 hours at 150 C'. The product was then cooled to 100 C., washed with water and dried in vacuo, and distilled. The color and color ill . 4 stability of the product were determined and the color values obtained are as follows:

The process is applicable to higher saturated fatty acids in general. Those derived from ordinary animal and vegetable fats and oils will contain from 8 to about 22 carbon atoms. The process may be applied to isolated saturated fatty acids and to selected fractions of the saturated fatty acids derived from fats or oils, or to complete mixtures of saturated fatty acids occurring in a fat or oil. v It will be apparent that other variations may also be made in the process without departing from the spirit of the invention.

We claim as our invention:

1. Process of treating higher saturated fatty acids which comprises mixing a small quantity of boron trifluoride with the fatty acid, heating the mixture to a temperature within the approximate range of -200 C. for a period of from 2 to 4 hours, thereafter washing the mixture with water to remove boron trifluoride, and distilling the residue to recover the fatty acid.

2. Process of treating higher saturated fatty acids which comprises mixin approximately /2 of 1% of boron trifluoride based on the weight of the fatty acid, with the fatty acid, heating the mixture to a temperature within the approximate range of -1'75" C. for a period of from 2 to 4 hours, therafter washing the mixture with water to remove boron trifluoride, and distilling the residue to recover the fatty acid.

3. Process of treating higher saturated fatty acids which comprises mixing approximately 1% of boron trifluoride ethyl ether complex based on the Weight of the fatty acid, with the fatty acid, heating the mixture to a temperature within the approximate range of 150-175 C. for a period of from 2 to 4 hours, thereafter washing the mixture with water to remove boron trifluoride, and distilling the residue to recovery the fatty acid.

DAVID E. TERRY. DONALD T. WARNER.

No references cited. 

1. A PROCESS OF TREATING HIGHER SATURATED FATTY ACIDS WHICH COMPRISES MIXING A SMALL QUANTITY OF BORON TRIFLUORIDE WITH THE FATTY ACID, HEATING THE MIXTURE TO A TEMPERATURE WITHIN THE APPROXIMATE RANGE OF 70-200* C. FOR A PERIOD OF FROM 2 TO 4 HOURS, THEREAFTER WASHING THE MIXTURE WITH WATER TO REMOVE BORON TRIFLUORIDE, AND DISTILLING THE RESIDUE TO RECOVER THE FATTY ACID. 